Police in Twin Falls, Idaho, say the suspect in a fatal shooting at a recently opened fast-food restaurant died from a self-inflicted gunshot wound. At a news conference, Twin Falls Police Chief Matthew Hicks said investigators are confident the gunman, identified as 24-year-old Chad Williams, acted alone during the Saturday attack.

Multiple reports say three people were killed and seven others were injured. Authorities state that two injured people were treated at a hospital and released, three were listed as stable, and two remained in critical condition.

Police also credit rapid actions during the incident with limiting further harm. Hicks said an off-duty state trooper and an armed citizen fired back at the suspect, helping divert him away from the restaurant. Police did not immediately disclose the identities of the off-duty officer or the bystander. Investigators say those actions helped prevent additional casualties, and the case remains under investigation.